Field of the Invention
The present invention relates to a heat exchanger for transferring heat of the first fluid (high temperature side) to the second fluid (low temperature side).
Background Art
There is demanded a heat collection technique from a high temperature gas such as a combustion exchange gas from an engine. As gas/liquid heat exchangers, fin-provided tube-type heat exchangers for an automobile radiator, an outdoor unit for an air-conditioner, etc., are general. However, for collecting heat from gas such as automobile exhaust gas, a general metal heat exchanger has poor thermal resistance, and the use at high temperature is difficult. Therefore, thermally resistant metal material and ceramic material having thermal resistance, thermal shock resistance, corrosion resistance, and the like are suitable. Though there is known a heat exchanger made of heat resistant metal, heat resistant metal has problems such as difficulty in processing, high density and heavy weight, and low thermal conductivity besides high cost.
Patent Document 1 discloses a ceramic heat exchanger where passages for a heating medium is disposed from one end face to the other end face with forming a passage for a medium to be heated in a direction perpendicular to a gap between the passages for a heating medium.
Patent Document 2 discloses a ceramic heat exchanger where a plurality of ceramic heat exchangers each having a heating medium passage and a non-heating medium passage are formed therein are disposed in a casing by means of a string-shaped sealing material made of an unfired ceramic material between bonding faces of the heat exchangers.
However, since Patent Documents 1 and 2 do not have good productivity because they have many steps such as plugging and slit forming, the costs are high. In addition, since the passages of gas/liquid are disposed on every other line, the piping structure and the sealing structure of the fluid are complex. Further, a heat transfer coefficient of liquid is generally 10 to 100 times larger than that of gas, and, in these techniques, heat transfer area on the gas side becomes insufficient, and the heat exchangers are large in proportion to the heat transfer area of the gas regulating the heat exchanger performance.
In Patent Documents 3 and 4, there is a tendency of increase in costs because the honeycomb structural portion and the tube portion have to be manufactured separately and then bonded together to have poor productivity.
Patent Document 5 discloses a honeycomb heat exchanger where a ceramic honeycomb for passing a low temperature fluid therethrough is bonded unitarily to the outer peripheral portion of a ceramic honeycomb for passing a high temperature fluid therethrough by means of a ceramic cylindrical body. Both the ceramic honeycombs are bonded together to make the heat exchange area of the fluids wide, thereby aiming at a high heat exchange amount. However, heat is transferred between the outer peripheral wall of the central honeycomb formed body and the outer peripheral wall of the outer peripheral ceramic honeycomb for exchange, and there is a ceramic cylindrical body between them to inhibit the fluids from being mixed upon breakage. Therefore, the heat exchange route is long, and the thermal resistance of the solid portion is large, which is considered to have a large loss of heat exchange.
Patent Document 6 discloses an apparatus for evaporating liquid by bonding ceramic honeycombs together. Since liquid passes along the minimum distance of the high temperature portion honeycomb, sufficient heat exchange cannot be conducted.
Patent Document 7 discloses a reaction container for conducting a uniform combustion heat generation reaction by air and a fuel with a catalyst on a ceramic honeycomb with a low pressure loss. The outside medium to be heated is not flowing, and it has a large loss of heat exchange.
Patent Document 8 discloses a heat exchanger where heat of the ceramic honeycomb is transferred to the outside, thereby lowering the gas temperature and generating steam. There is a phase transition from liquid to steam, and a strong structure for supporting the volume change is required.
Patent Document 9 discloses an exhaust heat recovery system using a ceramic honeycomb. However, the exhaust heat recovery system uses a heat acoustic phenomenon.
Patent Document 10 discloses an engine exhaust gas heat exchanger. In the heat exchanger, a catalyst conducting exhaust gas purification is a honeycomb structure, and heat exchange is conducted by the gas spouting portion at the back of the honeycomb structure and the fluid flowing in the periphery of the gas spouting portion.